From the prior art different electromechanical parking brake systems comprising at least one brake mechanism unit and at least one control device are known, in which in each case the at least one control device controls the actuation, i.e. the application and release of the brake mechanism unit for braking the vehicle. Such electromechanical parking brake systems will in future to an increasing extent replace by conventional, purely mechanical hand brakes and/or parking brakes of a vehicle.
Besides additional safety and comfort functions, an electromechanical parking brake system offers the possibility of determining the operating state by direct evaluation of the force-displacement-current characteristics of the brake mechanism unit, it being possible for the brake mechanism unit depending on the form of construction to be formed by a plurality of mechanical, electronic and/or electromechanical components. In particular, methods of determining system errors of such electromechanical parking brake systems by evaluation of the measured force-displacement-current characteristics are already known from the prior art.
If in particular the mechanical elements and/or brake components provided inside such an electromechanical parking brake system are new and therefore not stressed, then before the first start-up of such an electromechanical parking brake system it is necessary to carry out running-in and calibration of the electromechanical parking brake system.
Especially the brake mechanism unit or its mechanical components, such as for example a wrap springs, brake cables, brake linings etc., require a defined minimum extent of actuation to achieve the normal working range. By running in the electromechanical parking brake system is meant a first actuation of the fitted mechanical components to a defined minimum extent.
If such a minimum extent of actuation does not occur, then, when the electromechanical parking brake system disposed in the vehicle is actuated for the first time, extreme variations of the control parameters from the respective assigned control characteristic arise, which may be interpreted by the control device of the electromechanical parking brake system as system errors and therefore lead to a system failure.
Up till now, in order to avoid such system errors, electromechanical parking brake systems or their components after their manufacture and even before installation in the respective vehicle have been checked for their operating capability by means of suitable diagnostic methods and associated external diagnostic units, and in particular a running-in and calibration of the electromechanical parking brake system has been carried out. Furthermore, after a repair to the electromechanical parking brake system or the exchange of defective brake components a fresh running-in and calibration operation is to be carried out.
Via a corresponding diagnostic interface, which is optionally provided on the brake component to be checked, control commands externally generated by a diagnostic unit are transmitted to the electromechanical parking brake system and bring about an application and release of the brake mechanism unit. The result is a simulation of defined braking cycles or braking scenarios. The drawback of such external diagnostic methods is that they in no way take account of vehicle parameters that are critical with regard to safety, such as for example the vehicle velocity.